This invention relates generally to apparatus for aligning the wheels of motor vehicles. More particularly, the present invention relates to apparatus for aligning the wheels of motorcycles.
Routine rear wheel maintenance for motorcycles, such as tire changes, rear brake work, rear drive chain adjustments, require that the rear axle on which the rear wheel rides be positioned fore and aft such that the rear drive chain is tensioned to the recommended value. When the rear axle is properly positioned, the rear wheel tacks in-line with the front wheel and ideally in-line with the longitudinal frame (chassis) axis for optimum stability and performance.
Many motorcycles have built in provisions for front and rear wheel alignment. Such provisions generally consist of cast or stamped xe2x80x9cfixedxe2x80x9d reference lines on each side of the swinging arm and corresponding xe2x80x9cmoveablexe2x80x9d reference marks affixed to each end of the rear axle assembly. Where such alignment devices are provided, the rear wheel is properly mounted when the rear axle ends are adjusted fore and aft to obtain proper chain tension and the moveable reference marks on the axle ends are positioned at or near the corresponding fixed reference mark(s) on each side of the swinging arm.
These markings were considered a significant improvement years ago when they first started appearing on production motorcycles. However, over time it has been found that these markings are often not sufficiently accurate to provide adequate alignment of the front and rear wheels to ensure straight-line tracking for vehicle stability and rider safety. There inaccuracies are especially apparent in competition situations, where sustained high speeds and higher horsepower loads reveal chassis handling problems which are not as readily apparent during normal street riding. While the misalignment of wheels on a street riding machine might or might not cause noticeable chassis instability, these affects are greatly magnified on a closed circuit race course where the driver pushes a motorcycle to its design limits and sometimes beyond.
In order to perform a more accurate alignment of the front and rear wheels, most riders in competition use a rigid straight-edge device to affect alignment. The straight-edge device is placed along the front or rear tire sidewall chord such that it extends across the equivalent sidewall chord of opposite tire. The rear axle is typically adjusted fore and aft as required to provide proper chain tension and the wheel is adjusted such that the straight edge employed comes in contact evenly along said tire sidewall chords of each tire at two points (four total contact points ). While performing this alignment procedure, it is usually necessary to pivot the front wheel about its steering axis to obtain an assumed xe2x80x9cstraight-linexe2x80x9d position. The straight-edge alignment apparatus and the alignment procedure utilizing such apparatus are subject to several deficiencies.
Firstly, a straight-edge device having a sufficient length and stiffness is a burden to transport. In order to be of adequate length, the typical straight-edge device must be at least seven feet long. Therefore, the straight-edge device cannot be transported in all vehicles and special provisions for storing the device during transportation may be required. Since such apparatus is generally used for competitive racing which occurs at various remote closed course race tracks, portability of the apparatus is extremely important.
Secondly, a straight-edge device is difficult to use by one person working alone. The alignment procedure utilizing these devices requires adjustments of the front wheel about its steering axis and the taking of multiple measurements at several points along the chord of the front wheel. These measurements can become very subjective in nature due to the repetitive nature of checking, adjusting, rechecking, etc. that takes place during the alignment procedure. The points along the tire sidewall from which these measurements are taken may vary in practice due to this repetition.
Thirdly, using a straight-edge device on only one side of the motorcycle will align the front and rear wheels such that they are parallel but does not reliably align the wheels such that they are axially in-line with each other. Further, using a straight edge device on only one side of the motorcycle will not ensure that either wheel is axially in-line with the motorcycle chassis. Such an alignment often results in xe2x80x9cdogwalkingxe2x80x9d or xe2x80x9ccrabbingxe2x80x9d seen on streets or even racetracks. The only way to achieve an accurate and acceptable alignment of the wheels"" axis with each other and with the chassis longitudinal axis is to use the straight-edge device on both sides of the motorcycle. Performing the alignment procedure on one side of the motorcycle and then repeating the procedure on the other side of the motorcycle doubles the time which is required to perform the alignment and increases the measurement subjectivity.
Briefly stated, the invention in a preferred form is a portable alignment system for aligning the front and rear wheels of a motorcycle. The alignment system comprises front and rear wheel assemblies. The rear wheel assembly includes rigid, longitudinally extending, first and second alignment members. First and second laser units are removably mounted to the first and second alignment members, respectively. The front wheel assembly including rigid, longitudinally extending, third and fourth alignment members. At least one measuring indicia is removably mounted to each of the third and fourth alignment members. A rear clamping subsystem removably clamps the first and second alignment members on either side of the rear wheel of the motorcycle and a front clamping subsystem removably clamps the third and fourth alignment members on either side of the front wheel of the motorcycle during the alignment procedure. The first laser unit emits a laser beam onto the measuring indicia mounted to the third alignment member and the second laser unit emits a laser beam onto the measuring indicia mounted to the fourth alignment member to provide an objective indication of the degree of alignment of the front and rear wheels.
Each alignment member is a hollow, rectangular tube composed of a material and having a wall thickness which are selected to ensure that the tube is rigid over its length.
The first and second laser units are magnetically mounted on the outside surface of the front end portions of the respective alignment members. For alignment members composed of non-ferrous material, a mounting plate composed of ferrous material is mounted to the front end portions of the first and second alignment members.
Preferably, the measuring indicia are machinist style ruler segments composed of ferrous material. Four magnets are mounted at vertically and longitudinally spaced locations on the third and fourth alignment members such that the measuring indicia are magnetically mounted thereto.
The clamping subsystem may include multiple threaded rods and associated nuts and/or multiple hook and loop type cinch straps. A plurality of openings extend through the middle portion of each alignment member. One or two threaded rods may be inserted through opposed openings of the first and second alignment members and/or through opposed openings of the third and fourth alignment members and a nut threadably mounted on each end of the rods to clamp the alignment members to the associated wheel. A cinch strap may be engaged with the front and rear end portions of the opposed alignment members to mount a wheel assembly to a wheel. Alternatively, threaded rods and cinch straps may be used together to mount a wheel assembly to a wheel.
It is an object of the invention to provide a new and improved alignment system for aligning the front and rear wheels of a motorcycle.
It is also an object of the invention to provide a motorcycle alignment system which may be easily transported from one location to another.
It is further an object of the invention to provide a motorcycle alignment system which provides flexibility of use and which is relatively inexpensive to manufacture.
Other objects and advantages of the invention will become apparent from the drawings and specification.